Plastic screen for water well foot valves



Dec. 29, 1964 c. A. SALISBURY 3,163,229

PLASTIC SCREEN FOR WATER wm. FooT VALVES Filed June 25, 1962 TUE-4 @L'Arroz His United States Patent O 3,163,229 PLASTIC SCREEN FR WATER WELLFOOT VALVES Clifford A. Salisbury, Box '716, Tonlrawa, Okla. Filed June25, 1962, Ser. No. 204,782 6 Claims. (Cl. M6-234) The present inventionrelates to Huid strainers and more particularly, but not by way oflimitation, relates to an improved screen for the foot valve located onthe end of a tubing string in a water or other fluid well.

As is well known in the art, after a water well is drilled from thesurface into a water bearing stratum, the upperV strata are sealed offby a string of pipe known as the casing. The lower end of the well boreadjacent the water bearing sands is usually left open or the casing isprovided with large perforations to permit the water to seep into thecasing or well bore, as the case may be. In any event, relatively largeforeign particles such as chips of shale from the subsurface formation,rocks, leaves and other trash from the surface frequently find their wayto the bottom of the well bore. When a second string of smaller diameterpipe, known as the tubing string, is lowered through the casing stringto the water standing in the lower portion of the well bore, in order towithdraw the water, these foreign particles may enter the tubing stringand clog the pumping mechanism unless a suitable Screening device coversthe lower end of the conduit.

Screens heretofore provided in the art for the lower end of the tubingstring have been fabricated of a metal, such as brass, and usually havebeen attached to the conventional foot valve or check valve provided atthe lower end Vof the tubing string for maintaining the tubing stringfull of water so that a pump located at the surface will be primed andready for instant production. These screening devices have in most casesbeen made integral with the foot valve and perform the added functionofprotecting the downwardly projecting valve body guide stem of the footvalve. In any event, the metallic screens, even though fabricated frombrass, are subject to relatively rapid corrosion in many localities. Therigid metallic screens quite frequently are bunged-up as the tubing islowered through the casing. Further, should the tubing stringinadvertently be dropped or otherwise lowered so far as to contact thebottom of the well bore, the screen will usually be damaged to such anextent that the valve guide stem of the foot valve associated with Vthescreen will be bent and prevent operation of the foot valve. In morerecent times, the now common use of plastic hose for tubing has createda situation in which virtually none of the brass screens ever reach thebottom of the well bore without suffering damage. This is due to thefact that the plastic tubing is wound on a spool for storage andtransport. 'When the tubing is unwound from the spool, the plastictubing will invariably have a kink or sharp curvature at the lowerV endwhich will direct the lower end of the rigid metallic screen against thewall of the casing as the tubing is lowered into the well. The lower endof the screen then strikes each gap formed between the adjacent ends ofeach two joints of casing and is jammed, bent and quite frequently tornfrom the foot valve which it is designed to protect.

Therefore, it is a primary object of the present invention to provide ahighly flexible screen for connection to the foot valve or lower end ofthe tubing string which is virtually indestructible under normal usageand will withstand forces applied either laterally or axially along thescreen. The novel screen structure comprises, in general, a cup shapedbody of resilient plastic material having an annular rim portion at theupper end for connection around the end of a foot valve, a plurality ofgenerally ICC longitudinally extending ribs connected to the rim portionand extending downwardly, and a capvportion connected to the lower endof the ribs.

Another very important object of the present invention is to provide ascreen of the type described which is highly resistant to corrosionencountered in water wells and the like.

Yet another object of the present invention is to provide a screen ofthe type described which has virtually no resistance to fluid flowtherethrough and which thereby permits high efficiency of a suction typewater pump located at a surface.

Still another object of this invention is to provide a screen of thetype described and a foot valve, orother conduit, such that the screenmay be connected very quickly and easily to the foot valve and remainattached even when subjected to severe forces tending to tear the screenfrom the foot valve.

Many additional objects and advantages of the present invention will beevident to those skilled in the art from the following detaileddescription and drawings, wherein:

FIG. 1 is a side elevation, partially in section, of a screenconstructed in accordance with the present invention, the screen beingshown in combination with a foot valve for a water well which has beenmodified in accordance with the present invention;

FIG. 2 is an enlarged view of a portion of the cutaway View of FIG. land better illustrates the details of construction of the screen and thefoot valve to which the screen is attached;

FIG. 3 is a vertical sectional view of a string of casing showing theimproved screen in operative position on the lower end of a plastictubing string as the tubing string is lowered into a string of casing;and,

FIG. 4 is a vertical sectional view of the lower end of a well boreshowing the novel screen attached tothe lower end of a metallic tubingstring with the weight of the tubing string resting on the screen whichis inY contact with the bottom of the well bore.

Referring now to the drawings, and more particularly to FIG. 1, a screenconstructed in accordance with the present invention is indicatedgenerally by the reference numeral 10. The screen 10 comprises agenerally cup shaped body of resilient plastic material having anannular rim portion 12, a plurality of ribs 14, and a cap portion 16.The entire cup shaped body may be molded as a single unit from anytough, resilient plastic material which has appropriate corrosionresistant properties in the pal'- ticular fluid in which the screen isto be immersed and operated. However it is within the purview of thisinvention to utilize polyethylene which has been found to be especiallysuitable for molding the screen 10.

The screen l0 is illustrated in combination with the tubular body 18 ofa foot valve assembly which may be attached to the lower end of thetubing string of a Water well, as hereafter described in greater detail.The'foot valve should be of the type having no parts projecting belowthe lower end of the body 18, such as the foot valve described in mycopending application Serial No. 204,783 entitled Check Valve, tiled onluneY 25, 1962. The lower end 20 of the valve body 18 has a cylindricalouter lower surface 22 in which an annular groove 24 is machined. Theannular groove 24 preferably has a rectangular cross section, as bestseen in FIG. 2, so that the lower shoulder 26, in particular, as well asthe upper shoulder 27 will lie in a plane substantially perpendicular tothe axis of the tubular body 18. The rim portion 12 of the screen 10 issized to lit snugly around the cylindrical outer surface 22 of the valvebody 18 and is provided with an annular, inwardly projecting shoulder 28which extends, into the annular groove 24. The inwardly pro- PatentedDec. 29, i964` p r Y a Y jecting shoulder 28 may be rounded to provide across section, substantially as shown in FIG. 2, to increase the easewith which the screen may be telescoped over theV end ofthe foot valve.Even so, when the rounded annular shoulder 28 is insertedrin the squareannular groove 24, the rim 12 will function as a stout, resilient vbandtending to hold the shoulder 28 in place. Since the lower shoulder 26 ofthe groove 24 is perpendicular to the axis of the body 1S, the screen 10cannot be pulled from the end of the body 18 because no inclined surfaceis present to'exert a wedging force to expand the rim 12 and permit theshoulder 28 to leave the groove 24. For the Ysame reasons, the rimportion 12 cannot be forced further onto the cylindrical surface 22because ofthe square upper shoulder 27 of the annular groove 24.

' The ribs 14 are, preferably, approximately the same width as they arethick so as to have a generally square cross section. 'Ihis permits theribs to flex in' all direc tions with approximately equal ease andtendsto maintain the ribs equally spaced regardless of the direction fromwhich a distorting'force is applied to the screen.

cally =replaced and are considered expendable afterV one` use.

Referring now to FIG. 3, the screen 10 is shown attachedto the footvalve body 18 which in turn is connected to the lower end of a flexibleplastic hose 4t), as-

previously mentioned, which is frequently used as the tubing string inshallow water wells. Two joints 42 and 44 of Va casing string disposedin a well bore are interconnected by a conventional threaded collar 46,resulting inan annular gap 48 between the ends of the two joints of pipe42 and 44. The plastic hose 4G is shown as having a curl or kink at thelower end thereof as a result of storage on a conventional spool. As theplastic hose 40 is unreeled from the spool and lowered through thecasing, the foot valve body 18 and in particular the screen 10 connectedthereto will be directed against one wall of the casing. The lower endof the screen 1t) will thereby Also, the longitudinally extending spaces3l) formed be- Y tween each adjacent pair of ribs V14 are preferably ofap-v proximately the same width as each of the ribs 14.V In order forthe arca of the fluid passageway throughV the screen to be equal to thearea of the passageway through the tubular body 1S, the ribs should thenbe at least as long as the radius of the iiuid'passageway. However, inorder to provide the desired degree of liexibility, the ribs 14 arepreferably made approximately as long as the diame'ter of the rimportion 12. This will normally be approximately three timesl as-great asthe inside diameter of the tubing string so that the total crosssectional area of fluid passageways through the screen 10 will beatleast twice as great as the cross sectional area of the .fluidpassageways through the tubing, and in most cases be tween three andfour times as great, so as to oler very little comparative resistance tofluid liow and a corresponding low pressure drop `across the screen.

The cap portion 16 is preferably provided with a convex lower surface32. In order to increase the flexibility of the cap portion and reducethe quantity of plastic material used, the Vcap portion 16 may beconcavo-convex, substantially as shown in FIG.,1, and have a constantthickness preferably corresponding to the thickness of the ribs 14 andthe'rim portion 12.V The cap portion 16, as mentioned, is connected tothe lower endV of the ribs 14, and maintains the Vribs inspaced,rsubstantially parallel re-Y lationship, However, the cap portion16 preferably has a slightly smaller diameter than the rim portion 12 sothat the entire screen 10-has a slight downward taper. Thus it will benoted that any two ribs 14 ytaken in conibination with theinterconnecting portions of the rim portion 12 and the capvportion 16will approximate a parallelogram which contributes substantially to theflexibility and functionality of the/screen as hereafter described ingreater detail.

In operation the screen 10 is connected to the lowerr end of the tubingstring, such'as tothe body of the footV valve 18, merely by slipping therim portion 12 over the lower end 20 of the body 18. Even though the rimportion 12 may be of slightly less diameter than the lower .end 20, theresilient plastic material from which the screen 10 is molded willexpand su'iciently for'the rounded shoulder 23 to slipj over the end 20and still provide a tight fit around the cylindrical surface 22. whenthe annular shoulder 28fseats in the annularV groove-24. Once theannular shoulder 28 is in position in the annular groove 24, the squarelower and upper shoulders 26 and 27 will prevent the annular shoulder 28and the rim portion 12 from sliding longitudinally along the end 20 ofthe foot valve body 18 as previously described. Thus the be deformedsubstantially as illustrated inFlG. 3 due to contact of the cap portion16 with the wall of the joints screen 10 cannot be pulled from the footvalve body 18 or will not be jammed upwardly until a knife blade or thelike is inserted under the rim portion 12 and the an- 42 and 44. Thescreen 10 is readily deformable in the manner illustrated because of theflexibility of fthe plastic material from which' the screen is moldedand because of the fact that the ribs 14 in conjunction with the rimportion 12 andthe cap portion 16 form a number of parallelograms aspreviously described, which, as it is well known, are stable geometricfigures. However, since the ends of the ribs 14 are rigidly connected tothe rim portion 12 and to the cap portion 16, ythe ribs 14 will actuallyassume a slight S-shaped configuration substantially as illustrated inFIG. 3. It will be noted that the plane of the upper edge of the capportion 16 remains substantiallyV parallel to the plane of the rimportion 12 such that a line tangent to the convex curvature 32 of thecap portion 16 is vertical and coincides with the wall of the casingpipe. Therefore the rounded cap portion 16 of the screen 10 will easilyslide past the gap 48 without dangerof damaging the screen. Even thoughthe screen 10 will probably be pressed against the side of the casingafter it reaches the lower part of the well, untilthe weight of the footvalve body 18 straightens the plastic hose 40, and the area of theelongated slots 30 is somewhat reduced'by the distortion, the total areaof the openings will still be substantially greater than the crosssectional area of the hose 40 and fluid will still easily pass throughthe screen 10 with very little pressure drop. 1

FIG. 4 illustrates how the screen 10 collapses when a metal tubinglstring is inadvertently dropped against the bottom of awell bore 50 toprevent destruction. In FIG. 4 the foot valve body 18 to which thescreen 10 is connected is illustrated as threaded onto the lower end ofconventional metal tubing pipe 52 which of course has a substantialweight. In the event the tubing 52 is inadvertently dropped or otherwisebumped against the bottom of the well bore 50, thescreen 10 willassume'the position indicated. The convex'curvature 32 of the capportion 16 will readily permit the cap portion 16 to rotate or spinabout the vertically disposed longitudinal axis as it contacts thebottom 50 of the well bore so that the ribs 14 become twisted in anS-shaped configuration until the en-Y tire cup shaped' screen V10 iscollapsed. If the external diameter of the cap portion 16 is slightlysmaller than the internal diameter of the rim portion 12, the ribs 14and the cap portion-16 may be forced partially into the interior of thefoot valve body 18 such Vthat the likelihood of cut'- ting the ribs 14will usually be reduced. However, the cap portion'16 should not be madeappreciably less than the diameter of the passageway throughithe footvalve A will resume its original shape after a very short period oftime.

In the event the screen 1? should become clogged with material such asleaves or paper, suction acting on the clogging material may tend tocollapse the ribs 14 inwardly so long as suction is maintained by asurface pump. However, as soon as the pump is stopped to equalize thepressure, the resilient ribs 14 will spring back to their originalpositions and tend to dislodge the leaves or other clogging materialwhich might otherwise cling to and permanently clog a conventional rigidscreen. Therefore, the screen is to a very large degree self cleaning.

It will be obvious to those skilled in the art that the screen 10 can bevery economically molded as an integral unit in a conventional singlestep injection mold process so as to produce an exceedingly economicalscreen. Further, the screen lll may be securely connected to a suitable`foot valve body 18, or any other suitably adapted conduit, merely bytelescoping the rim portion 12 over the grooved end of the tubular body18. Experience has shown that the screen 10 will absorb compression fromvirtually any angle Without signiiicant harm and, in most cases, with noappreciable decrease in screening eciency. Further, even when compressedand distorted completely out of shape, in most instances the screeningdevice will still provide total fluid passageways at least as great asthe uid passageways of the tubular conduits to which Vthe device isattached.

Having thus described a preferred embodiment of the present invention,it is to be understood that various changes, substitutions andalterations can be made therein without departing from the spirit andscope of the invenftion as dened by the appended claims.

I claim:

1. A screen for a foot valve having a tubular body with a uid passagewaytherethrough, the screen comprising a generally cup shaped, axiallycollapsible body of resilient plastic material having an 'annular rimportion sized to fit tightly over the end of the tubular body; aplurality of flexible ribs connected at one of the ends thereof to therim portion, the unexed ribs extending in a generally parallelrelationship and being spaced apart to form elongated slots betweenadjacent ribs, and a circular, convexly curved cap portion connected tothe other of the ends of the ribs, the ribs being Vconnected to theperiphery of the cap portion.

2. A screen for a foot valve having a tubular body with a Huidpassageway therethrough as deined in claim l further characterized by aninwardly projecting annular shoulder within the rim portion for securingthe rim portion on the tubular body. Y

3; A screen for a foot valve having a tubular body. with a iiuidpassageway therethrough as defined in claim 1 wherein the ribs havesubstantially a square cross section.

4. A screen for a foot valve having a tubular body with a iluidpassageway therethrough as defined in claim 1 wherein the length of theribs is approximately equal to the diameter of the rim portion.

5. A screen for a foot valve having a tubular body with a iluidpassageway therethrough as defined in claim 4 wherein the cap portionhas a diameter less than thediameter of the rim portion.

6. A screen for a foot valve of the type having a tubular body with:a'uid passageway therethrough, said screen comprising an Vaxiallycollapsible, generally cup shaped body of resilient plastic material,said cup shaped body having anannular rim portion dimensioned to frictionally surround said tubular body;

a plurality of exible, resilient elongated ribs of substantially squarecross-section each connected at one of their ends to said rim portion incircumferentially `spaced rel-ation therearound, said ribs being spacedyvapart to form elongated slots between adjacent ribs;

and a circulan'convexly curved cap portion of smaller diameter than saidannular rim portion connected at its periphery to the other ends ofVsaid ribs with said ribs Vbeing connected to said cap portion lincircumfereutially spaced relation around the periphery thereof.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS724,368 8/42 Germany.

BENJAMIN HERSH, Primary Examiner.

1. A SCREEN FOR A FOOT VALVE HAVING A TUBULAR BODY WITH A FLUID PASSAGEWAY THERETHROUGH, THE SCREEN COMPRISING A GENERALLY CUP SHAPED, AXIALLY COLLAPSIBLE BODY OF RESILIENT PLASTIC MATERIAL HAVING AN ANNULAR RIM PORTION SIZED TO FIT TIGHTLY OVER THE END OF THE TUBULAR; A PLURALITY OF FLEXIBLE RIBS CONNECTED AT ONE OF THE ENDS THEREOF TO THE RIM PORTION, THE UNFLEXED RIBS EXTENDING IN A GENERALLY PARALLEL RELATIONSHIP AND BEING SPACED APART TO FORM ELONGATED SLOTS BETWEEN ADJACENT RIBS, AND A CIRCULAR, CONVEXLY CURVED CAP PORTION CONNECTED TO THE OTHER OF THE ENDS OF THE RIBS, THE RIBS BEING CONNECTED TO THE PERIPHERY OF THE CAP PORTION. 